An Analytical Chemistry Experiment in Simultaneous Spectrophotometric Determination of Fe(lll) and Cu(ll) with Hexacyanoruthenate(l1) Reagent M. C. Mehra and J. Rioux Universite de Moncton, Moncton, N. 6. Canada E1A 3E9 Principles of spectrophotometry and simultaneous multielement analyses are generally taught in an undergraduate instrumental chemistry course.' However, very few experiments embody the principle of simultaneous analysis of two or more elements in a mixture. In the course of our investieations we have come across a novel annlication of a reaction ;hat can headapted forsimultaneou~~nalysis of Fe(l1l) and Cutll! in a solution. The exnerimental conditionsare simnle and very few interferences'have been encountered from the common cations and anions. Since no preliminary sample preparations are needed, an analysis can be completed easily in a normal laboratory session. The method is based on selective interaction of the complex formed between Fe(II1) and Cu(I1) and potassium hexacyanoruthenate(I1) in acid solution. The former is purple blue (A max. = 550 nm), while the latter is pale green (A max. = 396 nm). Since the absorption characteristicsare very different, one can envisage a simultaneous analysis of these ions. Furthermore, thistechnique can he easiG extended toward the analysis of these species in environmental samples. Experimental Procedure Prepare a 0.0038 M potassium hexacyano~thenate(I1)solution by dissolving 1.77gof K&u(CN)Gin 1.00Lof double distilled water. Prepare by dilution Fe(II1)and Cu(1I) solutions at 10 ppm concentrations using their standardized 1000 ppm stock solutions. Prepare a buffer by mixing 900 mL of 0.02 Macetic acid with 100 mL of 0.02 M sodium acetate. Transfer 2 mL of the cyanoruthenate reagent and 10 mL of the buffer solution to a series of 26-mL volumetric flasks. Introduce aporooriate . . amounts of FdIII) . . solution to vield concentrations raneine .. .. from 0.04 2 ppm in the final wlurne. Simililrly,transirr ('urll! allq u o t i to
